Smart Tabs, will this solve this ,on a Whaler style boat???

[MONSTAFISHA]

I have a 16'Wahoo , the boat is similar to a 15'Whaler in style. I have recently removed a 45 hp Merc that was originally on the boat and put a 90hp Merc on it. <br />I have been having a problem with getting out of the hole , and porpoising. I know that the boat is somewhat stern heavy with the built in 15 gal. gas tank under the bench seat, battery in stern well, and me.<br />I changed the prop from 21"pitch aluminum to 16" Stainless, this REALLY solved hole-shot and brought the boat to its correct WOT @5500 rpms (it was running WOT @4700 rpms with 21"prop).BUT the porpoising is still happening when boat is on plane.<br />Will Smart-Tabs help this?????? At this point side to side balance and holshot are not an issue, just the porpoising.<br /><br />One other thing........The engine is already on the lowest hole and the cavitation plate is in the proper place when down, but because of the electric trim motor the engine cannot tuck all the way under

 

[DJ]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Smart Tabs will definetely help with both.

 

[Gary H NC]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Smart tabs really helped my porpoising problem.It took a couple adjustments after the first test run with them.I'm very happy with the way they made my boat handle.<br />Buy the (blems) they are fine and save about 60 bucks..<br />And Welcome Aboard!!

 

[Jdeagro]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Monstafisha;<br /><br />I will try not to get on my soap box, but.......<br /><br />The boat manufacturers have done a disservice to the consumer when it comes to small boats. They have directed the focus of performance and handling issues to the prop. However they will also tout their new and perfectly design hull as the ultimate.<br /><br />Boat balance and hull design is far more important than HP.<br /><br />The purpose of the propeller is to "propel". It should not be used to cure handling issues.<br />That is not to say you should ignore the prop and that you should not choose the correct prop for your set up, it simply means that there are other factors which impact the overall performance and handling of the boat as much or more than the power plant and prop.<br /><br />You went down 5" in pitch, which means that you either had a prop that was way off the mark to start with, or the boat was way out of balance, or both.<br /><br />The inability to control the porpoising even with a change of 5" in prop pitch, would indicate that the balance is way off.<br /><br />Will the Smart Tabs cure the problem? Without question! However your prop will likely need to be changed again as the motor is likely to run over the limit once you put the Smart Tabs on and get them tuned for your boat.<br /><br />Keep in mind that by moving down 5" in pitch you just down shifted from 3rd gear to 1st. Since you only have one gear, your gas consumption is going to increase.<br /><br />Use the ST1290-60 and prepare to move up in pitch.

 

[swist]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

I'm sure trim tabs will help, but it sounds to me like you are very stern-heavy, not just a little. Probably not much else you can do other than the tabs, although you might investigate moving the battery forward somewhere (this thing have a console?).

 

[steelespike]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

They sell or you can make wedges to put between the transom and motor so you can get more tuck.

 

[MONSTAFISHA]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Thanks for the replies......<br />John, These tabs will compensate for a lack of "tuck" in the engine and a stern heavy boat?? Do the smart tabs adjust so quickly as to outright prevent porpoising???? On propping, Im not adverse to going back to the original 21" or finding a 19", but do the smart tabs really substantially affect WOT too???<br /><br />Swist, the boat is probably 50lbs heavier in the stern, than the original set-up due to the difference in weight between a 45 and a 90 hp. I can move the battery under the console, and in fact I probably will, for the benefit of not worrying about water coming over the stern-well and shorting it out, but the battery cant be more than 40lbs, so that probably wont make much of a difference on the porpoising issue (although it cant hurt either). There really isnt anything else that can be shifted forward,and other than the motor everything is , as it was when the boat was new, nothing added or removed. <br />Spike, Im trying to avoid messing with the mounting of the motor mount , wedges may work, but it would be an easier task to put tabs on ....I think.<br />Gary , thanks for the heads up on blemishes

 

[Jdeagro]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Monstafisha;<br />Try to picture this: when the boat is at rest the tabs are deployed 25 degrees down, and upon acceleration the water pushes against the tab and up on the stern. In short it prevents the stern from dropping, and therefor the acceleration is near level. You do not need negative trim (any more than you have now) and the force or thrust of the motor will be used to propel the boat forward not up. The added efficiency of the motor / prop for forward thrust allows the boat to utilize more of the hull to raise it out of the water because the boat is running flat. Planing speed will be reduced because the tabs provide lift to the stern and the boat is more level, (more surface in the water. <br /><br />The porpoising is eliminated because the tabs continue to lift the stern (adjustable) and resist the bow rise. Trimming the motor down more also lifts the stern but at the cost of prop efficiency since the angle of the prop is incorrect (faces slightly up). The speed increase will come from a better prop angle, and smoother ride. Bouncing up and down creates a braking action and does not allow the boat to build speed.<br /><br />You will get a better ride and about 2 to 4 MPH improvement is speed. Choosing the correct prop will give you even more top speed, and even better fuel economy. <br /><br />There is no magic to this. The real problem is overcoming years of misconceptions regarding the differences between small boats (under 25' to 30') and larger ones. There is no difference!<br /><br />large boats need trim tabs to pane off and small ones do not. Why? Small boats have 2 1/2 times the power to weight ratio of their larger cousins. If trim tabs work on big boats with less than half the power to weight ratio, why would they not work on smaller boats with more HP?

 

[MONSTAFISHA]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

John<br />Thanks for the reply, I really appreciate you clarifying some things, it seems that almost EVERYONE on this forum RAVES about Smart Tabs, respectfully though, Im somewhat skeptical that these tabs will eliminate porpoising on this boat.Im not sure how to get rid of my skepticism about the effects of Smart-Tabs.......<br /><br />On my bigger boat , which is an inboard, I would be very unhappy if I didnt have trim tabs.On that boat, its not a correction for balance and weight, so much as it is a for the various sea/wind conditions .With this outboard ,on this particular boat it seems the purpose of having tabs would be totally different.<br /><br /><br />The bottom running surface where it meets the transom may not even have an area long and straight enough to put them on(from running strakes/bottom shape), so that, in itself may be a problem. I will try to post a pic over the weekend of the transom.<br /><br />For the price, and seemingly ease of installation, these would be an ideal solution, I just dont want to drill a bunch of holes to find out they didnt solve the problem

 

[stevens]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

How many testimonials from satisfied users do you need? The Smart Tabs do work as advertised and they will eliminate your porpoising. They did on my 21' daycruiser with an extra heavy inboard diesel engine.<br /><br />As for the fit, take a 12" ruler and hold it against the transom. Either you'll find a stretch of the hull where the ruler touches the hull all the way - or you'll see just how much you'll need to sand away, or how many washers you'll need between the hinge and the hull to compensate for the curve.

 

[Gary H NC]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

The strakes on the bottom of the hull won't affect the smart tabs..<br />I mounted mine centered of the strake.(if that makes any sense)...They work fine.<br />My old heavy boat jumps right up on plane now,stays on plane at MUCH lower speeds too..

 

[swist]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Moving a 40 lb battery may help more than you think - that's -40 in the stern and +40 in the console, an 80 lb weight distribtion change.

 

[MONSTAFISHA]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Thanks again for the replies, I do appreciate them. Im not normally this cautious when doing something to either boat especially when its not super-costly, but when it comes to adding holes in transoms , well, thats a different story.<br />In any case heres one pic of my boats transom line/bottom contour .....Im not sure where I would put these tabs, as there is no straight 12" line........???

<br /><br />

 

[stevens]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

I think you may be right - it's hard to see an obvious place to put tabs (any tabs) on this one, complicated further by the trailer bunks. My best guess would be as below, but that's probably not ideal either. NautiJohn should have an opinion on this...<br /><br />

 

[Tail_Gunner]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Well i too faced that bunk issue, gonna take a sawsall and remove the ends. After all they are not supporting anything.

 

[MONSTAFISHA]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

The Bunks dont bother me too much, as I can slide the boat back on the trailer by 4" with little to no consequence , other than removing the bunk overhang. I would be more concerned with the bottom angle in relation to any tabs

 

[stevens]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

<Bump> <br />NautiJohn?

 

[Jdeagro]

Re: Smart Tabs, will this solve this ,on a Whaler style boat???

Stevens;<br /><br />How are you doing?<br /><br />He can mount the Tabs up even though he does not have a perfectly flat area on the bottom. Just make sure that no part of the trim tab hinge / plat is below the bottom of the hull. He will need to straddle the cured surfaces.